Successive generations of compression schemes have increased the efficiency of video compression, particularly for camera-origin video with small differences between adjacent frames. However, detailed content with sharp edges (such as text) requires many high-frequency components to represent the content with high fidelity. Even under the most recent compression schemes a large number of bits are required to provide an accurate and satisfactory representation of the detailed content at a receiving device.
Bidirectional communication requires low-bitrate and low-latency coding. For a fixed bitrate, an encoder can either (1) spend more bits per frame on fewer frames per second, for high fidelity content that is desired to look sharp (e.g., text such as web pages, documents, spreadsheets, etc.), or (2) spend fewer bits per frame on more frames per second for high motion content (e.g., content for which motion representation takes priority over detail and sharpness such as camera-origin video, or highly animated graphics).
A combination of high fidelity and high motion content is typically communicated in a conferencing session between two or more users (e.g., an online video conferencing session, where high fidelity content (e.g. a PDF document) is presented simultaneously with a video collaboration window present on the screen presenting one or more of the participating users in the conference). During such conferencing, typically one channel of each of high fidelity and high motion content are transmitted, and the signaling and management of multiple channels adds complexity. The available bandwidth has to be split between the two kinds of content in a rigid way. The same problem arises in remote virtual desktop services, and conceivably in the rendering of semi-static interfaces alongside video content in any other kind of low-latency streaming service, such as broadcasting and gaming.